1. Field of the Invention
The present invention relates to a disc clamping device. More particularly, the present invention relates no a disc clamping device for selectively clamping a compact disc in a united device on which a mini disc MD and a compact disc CD can be loaded.
2. Description of the Prior Art
A disc player can be classified into a mini disc player, a compact disc player, and a laser disc player in accordance with the kinds of the discs, such as a mini disc, a compact disc and a laser disc, which are loaded on the disc player. Recently, there have Dean brisk studies for developing compatible disc players which can load any of variously sized discs in a selective manner.
Particularly, the studies have been concentrated on a disc clamping device by which two kinds of discs can be selectively loaded, and by which particularly a compact disc and a laser disc can be selectively loaded on a single turn table.
U.S. Pat. No. 4,841,517 (issued to Kurihara et al.) discloses a clamping device by which a compact disc and a laser disc can be selectively loaded on a single turntable of a disc player. In the above clamping device, as shown in FIG. 5A, a first hub 14 is inserted into a center hole of a compact disc 12, and then compact disc 12 is clamped on a turntable 10 by means of a second hub 16. In the meantime, as shown in FIG. 5B, second hub 16 is inserted into a center hole of a laser disc 18, and then, laser disc 18 is clamped on turntable 10 by means of a clamper 19.
Meanwhile, U.S. Pat. No. 4,853,924 (issued to Takahashi et al.) discloses another disc clamping device by which a compact disc and a laser disc can be selectively loaded on a single turntable of a disc player. In the above device, as shown in FIG. 6A, when a compact disc 22 is loaded, a first conical portion 25a (having a small diameter) of a hub 25 is inserted into a center hole of compact disc 22, and a magnet 27 of a clamper head 29 presses down compact disc 22 by the magnetic forces generated between magnet 27 and a turntable 20. As shown in FIG. 6B, when a laser disc 23 is loaded, a second conical portion 25b (having a large diameter) of hub 25 is inserted into a center hole of laser disc 23, and the bottom surface of clamper head 29 directly presses down laser disc 23 against turntable 20.
The above described devices can be applied only to a disc player in which a compact disc and a laser disc can be selectively loaded. However, the devices can not be applied to a disc player in which a mini disc is used. The reason is that generally a mini disc cannot be loaded in a naked form but can be loaded in an encased state in a mini disc cartridge and the above described devices cannot clamp the mini disc cartridge.
Therefore, there has arisen a necessity for a clamping device which is capable of clamping a mini disc and another disc being larger than the mini disc, such as a compact disc and a laser disc, selectively. However, no prior art for such a device has been found as far as the inventor knows.